The ISO rating reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

ISO rating

In photography, ISO is a means of specifying the 'speed' or sensitivity of a photographic film to light. Under the ISO system a doubling of the speed is represented by a doubling of the ISO number. ISO and ASA are functionally equivalent. Thus a 200ASA film is twice as sensitive as a 100ASA film.

This system contrasts with the DIN system where a doubling of the sensitivity increased the DIN number by 3. 100ASA film is roughly equivalent to a DIN number of 21.

This article is a stub. You can help Wikipedia by expanding it.

This is the "ISO rating" reference article from the English Wikipedia. All text is available under the terms of the GNU Free Documentation License. See also our Disclaimer.